Electric furnaces used in the refining of metals usually have a plurality of electrodes which are movable vertically through an opening in the furnace roof into and out of a bath of molten metal contained in the furnace. As material is added to or removed from the furnace, the level of the bath of molten metal within the furnace raises or lowers necessitating vertical movement of the electrodes in order that they may maintain a proper level with respect to the bath.
It is important that the opening in the furnace roof through which the electrode moves be sealed with respect to the electrode to prevent outflow of noxious gases during periods that the furnace operates under positive conditions when the internal pressure is greater than atmospheric pressure. Further, it is important to maintain an effective seal to prevent the inflow of cooling air resulting in undesirable cooling of the furnace interior when the furnace operates under negative conditions where the internal pressure is sub-atmospheric.
Various seal structure has been proposed for use with electric furnace electrodes. However, because of the high temperatures involved, uneven expansion of electrodes due to temperature differences along the length of the electrode, and difficulty in accurately forming electrodes, seal structure proposed to date has not been entirely satisfactory in use. In some instances the seal will tend to seize or bind with the electrode which can result in injury or damage to the refractory material making up the roof of the furnace when the electrode is raised or lowered. Further during periods of service, accumulations often tend to build up on the periphery of an electrode which increases any tendency of the seal to bind with the electrode.
Sealing structures have been proposed using weighted mechanical levers to force seal elements into contact with the periphery of an electrode so that the seal elements may move radially outwardly of the electrode against the force of the leveraged weights to accommodate change in diameter of the electrode or accumulation build up. However, because mechanical elements are utilized, they are susceptible to malfunctions often resulting in the sealing elements becoming jammed or stuck in place such that they bind against the electrode.
It is therefore an object of my invention to provide for an electrode seal surface which will include structure to assure a tight fitting seal with the periphery of an electrode and which at the same time will be able to move to accommodate uneven expansion of the electrode due to heat variation or to accommodate irregularities in the surface of the electrode due to build up of accumulations.
It is a further object of my invention to provide for an electrode seal which will include safety features to assure that there will be no damage imparted to the furnace roof in the event that, due to a malfunction in the seal, the seal might seize with the periphery of the electrode.